linux-kernel - [PATCH 08/12] mmc: reduce use of block bounce buffers

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Message-Id: <20180416085032.7367-9-hch@lst.de>
Date:   Mon, 16 Apr 2018 10:50:28 +0200
From:   Christoph Hellwig <hch@....de>
To:     iommu@...ts.linux-foundation.org, linux-arch@...r.kernel.org,
        linux-block@...r.kernel.org, linux-ide@...r.kernel.org,
        linux-scsi@...r.kernel.org, netdev@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH 08/12] mmc: reduce use of block bounce buffers

We can rely on the dma-mapping code to handle any DMA limits that is
bigger than the ISA DMA mask for us (either using an iommu or swiotlb),
so remove setting the block layer bounce limit for anything but bouncing
for highmem pages.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 drivers/mmc/core/queue.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
index 56e9a803db21..60a02a763d01 100644
--- a/drivers/mmc/core/queue.c
+++ b/drivers/mmc/core/queue.c
@@ -351,17 +351,14 @@ static const struct blk_mq_ops mmc_mq_ops = {
 static void mmc_setup_queue(struct mmc_queue *mq, struct mmc_card *card)
 {
 	struct mmc_host *host = card->host;
-	u64 limit = BLK_BOUNCE_HIGH;
-
-	if (mmc_dev(host)->dma_mask && *mmc_dev(host)->dma_mask)
-		limit = (u64)dma_max_pfn(mmc_dev(host)) << PAGE_SHIFT;
 
 	blk_queue_flag_set(QUEUE_FLAG_NONROT, mq->queue);
 	blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, mq->queue);
 	if (mmc_can_erase(card))
 		mmc_queue_setup_discard(mq->queue, card);
 
-	blk_queue_bounce_limit(mq->queue, limit);
+	if (!mmc_dev(host)->dma_mask || !mmc_dev(host)->dma_mask)
+		blk_queue_bounce_limit(mq->queue, BLK_BOUNCE_HIGH);
 	blk_queue_max_hw_sectors(mq->queue,
 		min(host->max_blk_count, host->max_req_size / 512));
 	blk_queue_max_segments(mq->queue, host->max_segs);
-- 
2.17.0